Blizzard send word that Diablo III sold 3.5 million copies in the first 24 hours on sale. They also point out: "That number does not include the more than 1.2 million players who received Diablo III as part of signing up for the World of Warcraft Annual Pass promotion." The upshot of that was 4.7 million people had the game on day one, and after a week that as grown to 6.3 million. That is a lot of copies of a videogame.
And this just in: I am the slowest-levelling barbarian ever. Still only level 16! Rubbish. I have got some excellent scythe-hammer things though, so all is well.